There’s just one small atom in this engine, but it’s one giant leap for mankind. Physicists have finally built the single-atom engine — a working engine that is made up of only one atom.
Previously, the best physicists could manage was an engine made up of 10,000 particles, according to Popular Mechanics.
The single-atom engine works in a similar way to a car engine, transforming thermal energy into mechanical energy. It is similar to a classic four-stroke car engine, which works by:
1. taking in a fuel mixture
2 compressing the fuel mixture using a piston
3. igniting the fuel
This pushes the piston back up, because the heat causes the fuel mixture to expand. It is this step that generates useful work since it is here that heating forcefully causes the piston to return to its original position (ie. thermal energy is converted into mechanical energy).
4. expelling exhaust
The new single atom engine, or nano-engine, follows a four-stroke process that closely parallels the classic car engine.
The atom is trapped in a cone of electromagnetic radiation. Physicists focus two laser beams on the cone. One beam heats the cone, and the other, applied closer to the base, uses Doppler cooling to cool it.
The particle is thus subjected to a thermodynamic cycle. It moves back and forth within the trap, thus “replicating the stroke of a typical engine.”
“Because this heating and cooling slightly changes the size of the atom (more exactly, it alters the fuzzy smear of probability of where the atom exists), and the cone fits the atom so snuggly, the temperature change forces the atom to race back and forth along the length of the cone as the atom expands and contracts.”
Johannes Roßnagel, the Ph.D. candidate who worked on the engine, encouraged people to imagine it “like a balloon in a funnel,”
“When you inflate the balloon, it will move towards the larger end of the funnel.”
The research team published a paper saying that their nano-engine can generate power of 10-22 watts. It operates at an impressive 0.3 percent efficiency.
“If the power of the single atom engine was scaled up from the tiny mass of an atom, its output would be equivalent to that of a car engine.”
Further experimentation with the single atom engine will allow researchers to learn more about thermodynamics at the single-particle level. Roßnagel’s team is planning to lower the operating temperature of the engine and investigate thermodynamic quantum effects. The team will cool the atom in their nano-engine further and confine it more tightly in its cone. The atom will then begin to behave more like a quantum wave-packet, and less like as a classical particle undergoing Brownian motion.
There are also plans to increase the power of the heat engine by linking it to a quantum heat bath.
“By reversing the cycle, we could even use the device as a single atom refrigerator and employ it to cool nano systems coupled to it.”
The study has been published in the latest edition of the journal Science. The researchers received some of their funding from the Volkswagen Foundation through the “Atomic nano assembler” project. The majority of funds were provided by the German Research Foundation project as part of the “Single ion heat engine” project.
Jean-Philippe Brantut, a cold-atom physicist at ETH Zurich, describes the nano-engine as “a major achievement” and a “milestone.” Brantut expressed his excitement about the future possibilities the single atom engine has opened.
“From this point onwards, they can really start to explore how thermodynamics behaves in contact with quantum mechanics, and that’s somewhere you have a lot of open questions.”
[Photo by Hulton Archive/Getty Images]